In a lot of the country, mosquito season is a tidy summer thing. South Texas does not play by those rules. Our long warm stretches and mild winters give mosquitoes a much bigger window, and in a warm year they barely take a break at all. Knowing when activity tends to surge, and why the season runs as long as it does here, helps you get ahead of the bites instead of chasing them.
Quick answer
In South Texas, mosquito activity typically picks up in March as temperatures climb past the low 70s, peaks through the hot, humid summer, and can stretch into November or later. With our mild winters, mosquitoes never fully disappear, which is why an early start on treatment keeps the whole season easier.
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The Temperature Trigger
Mosquitoes are cold-blooded, so their activity tracks the thermometer. They start getting going once temperatures settle consistently above the low 70s. Below about 50 degrees they go dormant. The warmer it gets, the faster they breed and the more aggressively they bite.
Around San Antonio, those low-70s days arrive early. That is why our season does not wait for summer. By the time it feels like patio weather, the mosquitoes are usually already active.
How the Season Plays Out Here
Spring is the ramp-up. As March warms and the spring rains fill every low spot and container, the first generations get going. Activity builds through April and May.
Summer is the peak. The combination of heat and humidity that defines a South Texas summer is ideal for fast breeding, and populations are at their highest. Then a warm, wet fall keeps things going well into October and November. A real cold snap finally slows them, but in a mild winter they never disappear entirely.
- Spring (March to May): activity ramps up with warmth and spring rain
- Summer (June to August): peak season, heat and humidity drive fast breeding
- Fall (September to November): activity stays high through warm, wet weather
- Winter: populations drop in cold snaps but rarely vanish in mild years
Why Rain Matters as Much as Heat
Temperature sets the pace, but water sets the numbers. Every rain refills the small containers, low spots, and clogged gutters that mosquitoes breed in, so a wet spring or a stormy stretch in summer can send the population spiking within a week or two.
That is why your worst weeks often follow heavy rain rather than just the hottest days. It also means a dry spell can quiet things down temporarily, only for the next round of storms to reset the count. Staying on top of standing water is a season-long job here, not a one-time chore.
Why Starting Early Beats Catching Up
The instinct is to call for help once the biting is already bad. The smarter move is to get ahead of it. Early in the season the population is still small, and knocking down those first generations keeps them from multiplying into the swarm you would otherwise be fighting by July.
A mosquito that does not get to breed in March is not the parent of a hundred more in April. Starting treatment as the season ramps up means fewer mosquitoes all summer and a yard that stays usable instead of one you are constantly trying to reclaim.
Year-Round Coverage in a Year-Round Climate
Because our season is so long, ongoing protection fits the climate better than a one-and-done spray. A recurring professional barrier treatment keeps the resting and breeding areas treated through the whole stretch, and some properties opt for service every three weeks during the worst of summer.
For continuous coverage, a trained technician returns on a regular schedule to retreat the resting spots and knock back the breeding sites before the population builds again. Either way, the goal is the same: stay ahead of a season that, in South Texas, hardly ever truly ends. Get started before the population peaks and the rest of the year takes care of itself.